Gene therapy strategies for the treatment of retinal disease have made major advances in recent years, in particular with the use of Adeno-Associated Virus (AAV) vectors. Indeed, AAV vectors are currently among the most frequently used viral vector for gene therapy aimed at inherited retinal disorders and for acquired disorders such as age related macular degeneration or diabetic retinopathy. AAV is regarded as the vector of choice for therapies because of its lack of pathogenicity, long-term gene expression following a single injection, and ability to infect the majority of retinal cells. AAV is a virus composed of a 4.7-kb single-stranded DNA genome enclosed within a 25-nm capsid. The tissue tropism and transduction efficiency of this virus depend on the capsid composition which allows initial receptor attachment, cellular entry, trafficking mechanisms and defines the selectivity for specific cells or tissues. The blood-retinal barrier minimizes systemic dissemination of the virus and the possibility of unwanted systemic side effects following intraocular delivery. Moreover, immune responses following intraocular vector administration are attenuated compared to those following systemic administration. An important limit to such therapy is that for most AAV serotypes intravitreal delivery results in poor retinal transduction, restricted to the inner retinal cells (mostly retinal ganglion cells and some Müller cells). The outer retina (photoreceptors and retinal pigment epithelium) harbor the majority of mutations leading to retinal degeneration. The only way to obtain AAV-mediated gene delivery to these therapeutically important cell-types has been the use of subretinal injection route. However, subretinal injection of AAV needs to make vitrectomy to create a needle hole through the retina and detach the photoreceptors from their supportive retinal pigment epithelium (RPE) with the injection of fluid, causing tissue damage at the site of injection. Three recent clinical trials for the retinal disease type 2 Leber's congenital amaurosis (LCA2) used subretinal injections to deliver AAV that carried the retinal isomerase-encoding gene RPE65 to the RPE; the trial protocol benefited from the atypical pathology of LCA2, which exhibits a loss of photosensitive function without significant structural disruption of retinal layers for many years (Jacobson et al., 2005, Bainbridge et al., 2008, Cideciyan et al., 2008, Maguire et al., 2008, Maguire et al., 2009). In contrast, most retinal degenerative diseases (including retinitis pigmentosa and macular degeneration, which account for half of all retinal degeneration cases) are characterized by the progressive loss of photoreceptor cells and increasingly fragile retinal architecture across the entire retina (Wright et al., 2010, Lin et al., 2009). In such disease states, subretinal surgery can induce mechanical damage, reactive gliosis, and loss of function (Nork et al, 2012). These procedural effects have even been documented in one LCA2 trial, as patients receiving a subretinal injection under the foveal region lost retinal thickness and visual acuity; these results led investigators to conclude that LCA gene therapy is efficacious in the extrafoveal retina but offers no benefit and some risk in treating the fovea (Jacobson et al., 2012). The lack of infection from the vitreous is due to low local concentrations due to diffusion in the vitreous as well as physical barriers to retinal penetration by the viral particles. It has been shown that AAV injected into the vitreous accumulates at the inner limiting membrane (ILM) in area where this membrane is disorganised or, diffuses away from the retina and that a mild digestion of the ILM enhances AAV transduction (Dalkara et al. 2009}. The ILM pose a barrier for the penetration of AAV into the retina from the vitreous in adults but this is the best route for AAV delivery.